The smallest jungle creatures are the scariest, according to a 'Planet Earth' producer

• BBC America's brand new series "Planet Earth II" just premiered in the US.• The third episode highlights the mind-boggling diversity of life in jungles.• Producer Dr. Emma Napper told INSIDER that she encountered a handful of deadly creatures behind the scenes.

Creating the "Jungles" episode of "Planet Earth II" was not easy. For one, jungles aren't very hospitable to television production. Expensive cameras and constant downpours don't exactly mix.

The second challenge is that jungles are literally crowded with life: They cover six percent of the earth's land but contain more than half its plants and animals. That means you're pretty likely to cross paths with a creature you weren't intending to meet — like, say, a deadly viper, or a spider as big as a dinner plate.

It's a good thing "Jungles" producer Dr. Emma Napper, a nature documentarian and biologist who used to study insects, stays cool under pressure. Napper told INSIDER that she and her crew encountered a slew of creepy-crawlies as they went about their daily shoots.

Constant rain = constant mosquitoes

Napper explained that the biggest challenge in making the episode was the weather. "Cameras don't like rain and it rains all the time," she said. "But just because you can't film, doesn't mean you can go back to base, so we spent a lot of time getting very wet. And that brings out the bugs too. [While filming] jaguars we had to sit still on the river bank in clouds of mosquitoes."

Jungle spider bites can have strange effects on humans.

Bioluminescent fungi glow in the Brazilian jungle.
BBC 2016

"It's not the jaguars that are scary," Napper said, referencing the episode's stunning sequence of jaguars on the hunt. "It's the small things. In the place where we filmed fungi and beetles, we found Brazilian wandering spiders."

The good news is that no one was bitten by the spiders. Even better: The crew forged ahead to film breathtaking time lapses of naturally glow-in-the-dark fungi like the one above.

Spiders also have no qualms about invading your clothes.

At one location in Brazil, the crew had to share a single room that happened to become infested with spiders. Napper recalled that spiders found their way inside mosquito netting and took up residence inside some of the crew members' clothes. In case that wasn't enough: Rats also ate through her underwear.

Deadly snakes are lurking everywhere.

A glass frog fights off a wasp in Costa Rica.
BBC 2016

"We came across snakes a few times," Napper said. It's always a little scary as you don't tend to see them until you are nearly treading on them, and of course many of them are deadly. I felt very sorry for the cameraman who beautifully shot the glass frogs and shared the pond he was standing in with a fer de lance!" (That's a venomous viper common in Central America.)

Napper herself had a close brush with a deadly snake, too.

"One evening after crouching down in the undergrowth for a few hours next to a patch of fungi, I got up and moved a filming stand next to me and out slithered a 60-centimeter long coral snake! One bite can kill! Luckily we all stayed calm, including the snake, and backed away with no harm done."

But the episode's triumphs were worth the close encounters.

A young spider monkey snacks on leaves in Guatemala.
BBC America/Emma Napper

The "Jungles" episode features a diverse cast of characters: A young spider monkey learning to navigate the canopy, flying Draco lizards, hummingbirds with bills longer than their bodies, and worms that glow after dark.

The crew even got rare footage of Araguaia river dolphins, who live in the flooded jungles of Brazil. The species was only discovered in 2014, and virtually nothing is known about them. But Napper and her crew — aided by a drone — were able to capture 15 minutes of footage the dolphins in murky water.

Meet all these creatures (and more!) in the "Jungles" episode of "Planet Earth II." It airs March 4 at 9 p.m. on BBC America.